## Sound - Detailed Help

### Assignment SM2: Characteristics of Sound Waves

Objectives:
• The student should be able to identify and describe the characteristics of amplitude, wavelength and frequency for a sound wave.
• The student should be able to identify factors effecting (and not effecting) the speed of a sound wave.

The Physics Classroom, Sound and Music Unit, Lesson 2, Part a

 High intensity sounds are observed as relatively loud sounds. The sound waves which are most intense and perceived as loud sounds are those which have a _____. Identify the one characteristic which is unique of such sound waves. Amplitude, Intensity and Energy: The intensity of a wave is the rate at which energy passes through a cross-sectional area of the medium. Intense waves are associated with relatively large amplitude of vibrations of the particles of the medium. The more energy put into the wave by the source, the greater the amplitude of vibration of the particles, and the greater the intensity of the wave. A holler is clearly perceived differently than a whisper. In a holler, particles of the medium are disturbed a relatively large amount from their resting position. A holler causes particles to vibrate about their rest position with a relatively large amplitude of vibration. The result is a relatively high intensity sound wave. At the observer's ear, particles of the medium are undergoing a relatively high amplitude vibration. Such vibrating particles will transmit a relatively high intensity wave to the ear. In turn, the observer perceives the sound wave to be loud.

 High-pitched sounds are characterized by sound waves which have a _____. List all that apply ... . Definition of Pitch: Pitch is the sensation of an observer to a sound's frequency level. A high frequency sound wave is perceived to be a high pitch sound. A low frequency sound wave is perceived to be a low pitch sound. The speed (v) of a wave can be calculated from knowledge of the wavelength () and the frequency (f) of the wave. The formula is: v = f • The frequency (f) of a wave and the period (T) of a wave are mathematically related by the following formula: f = 1 / T As stated in the Define Help section above, pitch is directly related to the frequency of a sound. But pitch might be related to other wave properties as well. After all, the frequency of a wave is inversely related to the wavelength of a wave and inversely related to the period of a wave. (See Formula Fix section above.) So relatively high frequency sounds are also relatively low wavelength sounds and relatively low period sounds.

 A sound wave is traveling through a medium. The diagram below depicts the presence and location of the particles at a given instant in time. Utilize the ruler to determine the best approximation of the wavelength of the wave. The wavelength is ____ units. As a sound wave travels through a medium, particles of the medium undergo vibrations about their resting position in a direction which is parallel (and anti-parallel) to the direction the wave moves. This longitudinal motion results in the formation of compressions and rarefactions. The diagram represents the location of the particles of the medium at a given instant in time. The familiar pattern of alternating compressions and rarefactions are clearly seen in the diagram. Definition of Wavelength: The wavelength of a wave is the length of the wave or repeating wave segment. For transverse waves, it is often represented as the distance from a crest to the next adjacent crest. For longitudinal waves, it is often represented as the distance from a compression to the next adjacent compression. A centimeter ruler is provided on the diagram to assist in measuring the length of the repeating pattern. Starting in the middle of any of the compressions, measure to the next adjacent compression. The distance from compression to compression is the wavelength. One wise measurement strategy is to make a two or more measurements to insure that you have the same approximate measurement of wavelength. Pick the closest answer; and if none of the answers are even close, you might try measuring again.

 Some sound waves have short wavelengths and others have long wavelengths. Suppose a comparison is made of two sound waves of varying wavelengths traveling through the same medium. The long wave can be certain to also have a relatively ____. List all that apply ... . Factors Affecting Wave Speed: The speed of a wave is dependent upon the properties of the medium through which the wave is moving. An alteration in the properties of the medium will result in a change in the speed at which the wave moves through that medium. The speed (v) of a wave can be calculated from knowledge of the wavelength () and the frequency (f) of the wave. The formula is: v = f • The frequency (f) of a wave and the period (T) of a wave are mathematically related by the following formula: f = 1 / T In comparing a long wave and a short wave, a long wave is a wave of greater wavelength. If both travel through the same medium, then each would travel at the same speed (v). See Physics Rules section above. The wavelength, frequency and speed are related by the wave equation (see Formula Fix section). For the same speed, a long wave would have a lower frequency. And a lower frequency would be associated with a greater period.

 Several sounds waves travel through the same sample of air. A fast sound wave would be the wave that ____. Factors Affecting Wave Speed: The speed of a wave is dependent upon the properties of the medium through which the wave is moving. An alteration in the properties of the medium will result in a change in the speed at which the wave moves through that medium. Click the button below to play an audio file in a separate window. Your browser does not support the audio element. Please download and view here. The speed of a wave is often calculated as the product of frequency and wavelength. This gives many students the wrong impression that the speed of a wave depends upon frequency and wavelength. But don't be fooled! The speed of a wave is independent of its frequency and wavelength. A high frequency sound wave is not necessarily a high speed sound wave. A high frequency sound wave is a low wavelength sound wave. The speed of the sound wave simply depends upon the properties of the medium through which the wave is traveling. Making the frequency bigger will only cause the wavelength to become smaller. If there are several sound waves traveling through the same sample of air, then there is one thing that you can be sure of. Each of the sound waves is traveling with the same speed. After all, if the speed of a wave is dependent solely upon the properties of the medium, then all waves which travel through a particular medium will travel through it at the same speed. Alterations in wave properties (amplitude, intensity, frequency and wavelength) will not alter the speed of a wave.

 Altering the _______ will be sure to result in an alteration of the speed of the sound wave. List all that apply ... . Factors Affecting Wave Speed: The speed of a wave is dependent upon the properties of the medium through which the wave is moving. An alteration in the properties of the medium will result in a change in the speed at which the wave moves through that medium. The speed of any wave is calculated as the product of frequency and wavelength. This gives many students the wrong impression that the speed of a wave depends upon frequency and wavelength. But don't be fooled! The speed of a wave is independent of its frequency and wavelength. A change in the frequency value will not result in a change in the speed value. Rather, changing frequency will result in a change in the wavelength in such a manner that the speed value turns out the same. While the speed can be calculated from knowledge of the frequency and wavelength, its value is unaffected by changes in frequency and wavelength. As discussed in the Physics Rules section above, the speed of a wave is dependent upon the properties of the medium through which it is traveling. Only by altering the properties of the medium can the speed of the wave be altered. Click the button below to play an audio file in a separate window. Your browser does not support the audio element. Please download and view here.

 TRUE or FALSE: A loud sound has a greater speed than a soft sound. Yelling loud would make a sound wave travel measurably faster. (Note: The actual true-false statement is randomly selected from a collection of statements and may differ from the one shown above.) Factors Affecting Wave Speed: The speed of a wave is dependent upon the properties of the medium through which the wave is moving. An alteration in the properties of the medium will result in a change in the speed at which the wave moves through that medium. Many students are under the impression that the speed of a wave is dependent upon the properties of a wave. For instance, some believe that a more intense wave will travel faster than a less intense wave. That is, a holler will travel through air at a faster speed than a whisper. But don't be fooled! The speed at which sound waves travel through air is dependent upon the properties of the air - mainly the temperature. Only by altering the properties of a medium can the speed of sound be altered. Click the button below to play an audio file in a separate window. Your browser does not support the audio element. Please download and view here.

 Sound wave A and sound wave B are simultaneously traveling through the auditorium. Wave A has twice the frequency as wave B. Thus, the wavelength of wave A will be _____ the wavelength of wave B and the speed of wave A will be ____ the speed of wave B. Factors Affecting Wave Speed: The speed of a wave is dependent upon the properties of the medium through which the wave is moving. An alteration in the properties of the medium will result in a change in the speed at which the wave moves through that medium. Click the button below to play an audio file in a separate window. Your browser does not support the audio element. Please download and view here. Wave A and wave B are both traveling through the same medium - the air in the auditorium. As discussed in the Physics Rules section above, the speed at which sound waves travel through the air in the auditorium is dependent upon the properties of that air (mainly the temperature of the air). Since both waves are traveling through the same air, their speed will be the same. The connection between speed, wavelength and frequency is stated in the Formula Fix section below. If the v in the equation is the same for both wave A and wave B, then the product of frequency and wavelength must be the same for both waves. The wave with the greatest frequency will have the shortest wavelength. In fact, the ratio of their frequencies will be inversely related to the ratio of their wavelengths. The speed (v) of a wave can be calculated from knowledge of the wavelength () and the frequency (f) of the wave. The formula is: v = f •

 Doubling the frequency of a sound wave within a uniform (unchanging) medium will _____. List all that apply ... . Factors Affecting Wave Speed: The speed of a wave is dependent upon the properties of the medium through which the wave is moving. An alteration in the properties of the medium will result in a change in the speed at which the wave moves through that medium. Click the button below to play an audio file in a separate window. Your browser does not support the audio element. Please download and view here. The speed (v) of a wave can be calculated from knowledge of the wavelength () and the frequency (f) of the wave. The formula is: v = f • As discussed in the Physics Rules section above, the speed at which sound waves travel through a medium is dependent upon the properties of that medium. If the medium is not changed (described as being uniform), then the wave speed is not changed. Yet doubling the frequency must alter something. The connection between speed, wavelength and frequency is stated in the Formula Fix section above. The left side of the equation (v) is the constant quantity. Thus, the product of frequency and wavelength must remain constant. A doubling of the frequency must be accompanied by a halving of the wavelength in order for their product to remain constant.